Autopilot design of bank-to-turn missiles using state-space disturbance observers

Robust autopilot design for bank-to-turn missiles under disturbances and uncertainties is investigated in this paper using the disturbance observer concept. In this setting, the influences caused by parameter variations are merged into a disturbance term and regarded as a part of the lumped disturbances. Disturbance observers are employed to estimate the lumped disturbances. However, the lumped disturbances may not satisfy the so called "matching" condition, i.e., acting on the same channel as the control inputs. The existing disturbance observer based control schemes are not able to cope with "mismatching" disturbances. By properly designing disturbance compensation gain vectors in the composite control law, a disturbance observer based robust control method is proposed in this paper to counteract the "mismatching" disturbances and the influences of parameter variations from output channels of the BTT missile system. Simulation results show that the proposed method obtains promising disturbance attenuation ability and robustness against model uncertainties.